Dear Jiashen, 1. *First question: Line resistance* If you notice the last part of of Carlos's response to your question, it has the answer; * * *"The model used in Matpower is the standard pi one-line equivalent of a three phase transmission line, with quantities in per-unit. This is constructed from a base voltage equal to sqrt(3) times the phase voltage and a base power equal to three times the per-phase power. With this choice of base quantities, the base impedance is equal to the per-phase impedance. This is covered in most power systems analysis textbooks." *
What Carlos is trying to explain is that the pi one-line equivalent is per phase, and so are resulting values. My understanding is that MATPOWER is modeled in such a way that* *the resistance values are '*for only one of the three conductors' *i.e. per phase. 2. *Second question: Line rating* For the line rating, in my own understanding the line ratings are based on 3-phase values, i.e.* '**the total rating for 3 conductors connected in parallel'* . All the best On 12 July 2013 10:25, Jiashen Teh <[email protected]> wrote: > Dear Carlos, > > Thank you for pointing out, however, can you tell me what's the answer to > my questions? > > Yours sincerely, > > Jiashen Teh > PhD Student > Electrical Energy & Power Systems Group, School of Electrical & Electronic > Engineering > Ferranti Building (B18), The University of Manchester, M13 9PL, United > Kingdom > Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 792 322 4864 > ________________________________________ > From: [email protected] [ > [email protected]] on behalf of Carlos E > Murillo-Sanchez [[email protected]] > Sent: 12 July 2013 02:01 > To: MATPOWER discussion forum > Subject: Re: conductor resistance and power rating (MVA) > > Dear Jiashen: > > The model used in Matpower is the standard pi one-line equivalent of a > three phase transmission line, with quantities in per-unit. This is > constructed from a base voltage equal to sqrt(3) times the phase voltage > and a base power equal to three times the per-phase power. With this > choice of base quantities, the base impedance is equal to the per-phase > impedance. This is covered in most power systems analysis textbooks. > > carlos. > > Jiashen Teh wrote: > > Dear Dr Ray, > > > > Before asking my question, allow me to put us on the same level of > > understanding. > > If I am not mistaken, each transmission line in reality is actually > > consists of 3 conductors connected in parallel. > > > > Hence, these are my 2 questions based on the above assumption: > > > > The resistance values in Matpower are > > (a) the total resistance of 3 conductors connected in parallel? > > or > > (b) the resistance for only one of the three conductors? > > > > > > The line ratings in Matpower are > > (a) the total rating for 3 conductors connected in parallel? > > or > > (b) the rating for only one of the three conductors? > > > > > > Yours sincerely, > > > > Jiashen Teh > > PhD Student > > Electrical Energy & Power Systems Group, School of Electrical & > > Electronic Engineering > > Ferranti Building (B18), The University of Manchester, M13 9PL, United > > Kingdom > > Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 792 322 4864 > > > > > -- *Fred Kanjelesa. *Zambia/Lusaka. Mobile: +260967880912 "Go as far as you can see. When you get there, you'll be able to see farther!" *Thomas Carlyle* ** ****
